This invention relates to supramolecular polymers that comprise self-complementary quadruple hydrogen bonding units (4H-units) that are capable of forming (at least) four H-bridges with other of such units leading to physical interactions between different polymer chains. Self-complementary hydrogen bonding units having at least four hydrogen bonds in a row, and thus capable of forming at least four hydrogen bonds, are in this patent application abbreviated as quadruple hydrogen bonding units, quadruple hydrogen bonding sites, 4H bonding units, 4H-units, 4H-elements or structural elements (4H) and are used in this patent application as interchangeable terms. Sijbesma et al. (U.S. Pat. No. 6,320,018; Science, 278, 1601; incorporated by reference herein) discloses such self-complementary units which are based on, particularly, 2-ureido-4-pyrimidones.
Telechelic polymers or trifunctional polymers have been modified with 4H-units (Folmer, B. J. B. et al., Adv. Mater. 2000, Vol. 12, 874; Hirschberg et al., Macromolecules 1999, Vol. 32, 2696; Lange, R. F. M. et al, J. Polym. Sci, Part A, 1999, 37, 3657-3670). However, these polymers have the 4H-unit coupled at the termini of the polymers, so the number of end groups is therefore limited to two, and the functional units are always located at the periphery of the polymer. Moreover, these polymers are not, or only poorly, water-soluble.
WO 02/46260 discloses polyurethane based polymers with 4H-bonding units as end-cappers and, optionally, with grafted 4H-bonding units; the disclosed polymers can be used as hot melt adhesive or TPU-foam. WO 03/099875 discloses polyurethane based polymers with 4H-bonding units as end-cappers that can be used as TPU-foam. Both patent applications use comparable or the same chemistry as described in Lange, R. F. M. et al, J. Polym. Sci, Part A, 1999, 37, 3657-3670, and are not water-soluble or dispersible.
WO 04/016598, incorporated by reference herein for the US patent practice, discloses polymers with grafted quadruple hydrogen bonding units. For example, polyacrylates and polymethacrylates with grafted 4H-units have been produced using different kinds of polymerization techniques. However, the 4H-units are not integrated in the backbone, and more importantly, no water soluble or water dispersible ionomers are disclosed.
WO 04/052963, incorporated by reference herein for the US patent practice, disclose polysiloxanes comprising 4H-units in the polymer backbone. However, these polymers do not contain ionic groups and are not water-soluble/dispersible.
WO 05/042641, incorporated by reference herein for the US patent practice, discloses polymers comprising 4H-units in the polymer backbone. However, these polymers do not contain ionic groups and are not water-soluble or dispersible.
US 2004/023155, incorporated by reference herein for the US patent practice, discloses a supramolecular polymer having the structure A-L-B, wherein A and B are polymers comprising a 4H-unit (in US 2004/023155 the 4H-unit is indicated by “QHB”) which are linked by joining group L. The preparation of polymers A and B is said to be possible by reacting an appropriate polymer with a 4H-unit precursor having a terminal isocyanate group (in US 2004/023155 indicated by “QHBE”). According to US 2004/023155, an appropriate polymer would be a carboxyl substituted acrylic polymer such as a (co)polymer of acrylic acid. According to the examples (Examples 12 and 13), the 4H-units are grafted in a post modification step onto the carboxyl substituted acrylic polymers so that the 4H-units do not constitute an integral part of the polymer structure and are not present as terminal groups. US 2004/023155 further discloses that the appropriate polymer may be a polyurethane made from carboxyl functional diols, e.g. dimethylol propionic acid, and diisocyanates. Such polyurethanes comprising anionic groups would have a terminal OH-group that can me postreacted with the 4H-unit precursor having a terminal isocyanate group thereby providing a polyurethane comprising anionic groups which has a terminal 4H-unit. However, US 2004/023155 does not provide an enabling disclosure of such modified polyurethanes.
Because of environmental regulations governing the emission of volatile organic compounds (VOCs) into the atmosphere, the need for waterborne systems is emerging. General ways to obtain polyurethane ionomers, i.e. polyurethanes containing ionic groups that are dispersible or soluble in water, are for example described by Dieterich, D. et al., Angew. Chem., 1970, Vol. 2, page 53. In U.S. Pat. No. 3,480,592 and U.S. Pat. No. 3,388,087, polyurethanes are disclosed that are water dispersible by the incorporation of cationic-groups in the polyurethane chain. In order to obtain elastic materials, however, these polyurethanes need to be chemically cross-linked or of high molecular weight. Especially the cross linked materials can hardly be processed, if at all.
The present invention discloses polymers that not only contain 4H-units in their molecular structure, but also ionic or ionogenic groups. It has surprisingly been found that the presence of cationic or anionic groups in the polymer chain does not disturb the supramolecular hydrogen-bonding interactions between different 4H hydrogen bonding units. Nor does the presence of the apolar 4H-units hinder the water solubility or dispersibility of the resulting polymers. Even more surprising is the fact that the possible remaining water molecules in the dried materials do not corrupt the hydrogen-bonding interactions and that therefore the resulting waterborne materials still display unique material properties, because of the reversible nature of the H-bonding interactions between the polymer chains. Thus, the present invention enables the manufacture of elastic, non-tacky polymers with excellent film-forming properties that can easily be processed or applied, by for example spraying, from high solid content—yet still low viscosity—water dispersions (or solutions). The described polymers are of relatively low molecular weight, thereby circumventing the use of hardly processable high molecular weight or cross-linked materials.